## Compose sample application
### Java application with Spring framework and a Postgres database
Project structure:
```
.
├── backend
│ ├── Dockerfile
│ └── ...
├── db
│ └── password.txt
├── docker-compose.yaml
└── README.md
```
[_docker-compose.yaml_](docker-compose.yaml)
```
version: "3.7"
services:
backend:
build: backend
ports:
- 8080:8080
db:
image: postgres
...
```
The compose file defines an application with two services `backend` and `db`.
When deploying the application, docker-compose maps port 8080 of the backend service container to port 8080 of the host as specified in the file.
Make sure port 8080 on the host is not already being in use.
## Deploy with docker-compose
```
$ docker-compose up -d
Creating network "spring-postgres_default" with the default driver
Building backend
Step 1/11 : FROM maven:3.5-jdk-9 AS build
3.5-jdk-9: Pulling from library/maven
...
Successfully tagged spring-postgres_backend:latest
WARNING: Image for service backend was built because it did not already exist. To rebuild this image you must use `docker-compose build` or `docker-compose up --build`.
Creating spring-postgres_backend_1 ... done
Creating spring-postgres_db_1 ... done
```
## Expected result
Listing containers must show two containers running and the port mapping as below:
```
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
56236f640eaa postgres "docker-entrypoint.s…" 29 seconds ago Up 28 seconds 5432/tcp spring-postgres_db_1
6e69472dc2c0 spring-postgres_backend "java -Djava.securit…" 29 seconds ago Up 28 seconds 0.0.0.0:8080->8080/tcp spring-postgres_backend_1
```
After the application starts, navigate to `http://localhost:8080` in your web browse or run:
```
$ curl localhost:8080
Getting Started: Serving Web Content
Hello from Docker!
```
Stop and remove the containers
```
$ docker-compose down
Stopping spring-postgres_db_1 ... done
Stopping spring-postgres_backend_1 ... done
Removing spring-postgres_db_1 ... done
Removing spring-postgres_backend_1 ... done
Removing network spring-postgres_default
```